Thermal load balancing systems and methods

ABSTRACT

Systems and methods for implementing thermal load balancing are disclosed. In an exemplary embodiment, a thermal load balancing system for a multiprocessor computer having a plurality of processors may comprise a heat sink network having a plurality of local heat sinks. The local heat sinks are thermally coupled to separate processors in the multiprocessor computer. At least one heat pipe thermally couples each of the plurality of local heat sinks in the heat sink network.

TECHNICAL FIELD

The described subject matter relates to thermal management, and moreparticularly to thermal load balancing systems and methods.

BACKGROUND

Electronic devices generate heat during operation. Indeed, computersystems (e.g., server computers) are now commercially available withmultiple processors, thereby generating even more heat thansingle-processor computer systems. Accordingly, heat dissipationcontinues to be a concern in the development of computer systems andother electronic devices. If not properly dissipated, heat generatedduring operation can shorten the life span of various electroniccomponents and/or generally result in poor performance.

Various thermal management systems are available, and typically includea heat sink and/or a cooling fan. The heat sink is positioned adjacentthe electronic components generating the most heat (e.g., the processor)to absorb heat. A cooling fan may be positioned to blow air across theheat sink and out an opening formed through the computer housing todissipate heat into the surrounding environment. However, cooling fanstake up space within the computer housing and tend to be noisy.

In addition, various processors in a multiprocessor system, even beingidentical to one another, may operate at different frequencies andgenerate more or less heat at various times during operation. Sizing theheat sink and/or cooling fan based on average operating frequencies mayresult in the system overheating if any processor exceeds averageoperating frequencies for an extended time. However, sizing the heatsink and/or cooling fan based on a worst-case scenario results in heatsinks that are too big (and therefore heavy and space consuming) and/orcooling fans that are too noisy for typical operation.

SUMMARY

An exemplary thermal load balancing system for a multiprocessor computerhaving a plurality of processors may comprise a heat sink network havinga plurality of local heat sinks. The local heat sinks are thermallycoupled to separate processors in the multiprocessor computer. At leastone heat pipe thermally couples each of the plurality of local heatsinks in the heat sink network.

In another exemplary embodiment, thermal load balancing may beimplemented as a method, comprising: absorbing heat from each processorin a multiprocessor computer at local heat sinks, and distributing heatfrom the local heat sinks over a heat sink network to substantiallybalance thermal loading on the local heat sinks.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a high-level schematic illustration of an exemplary printedcircuit board which may implement thermal load balancing.

FIGS. 2-4 are high-level schematic illustrations of other exemplaryembodiments of thermal load balancing.

DETAILED DESCRIPTION

Briefly, thermal load balancing systems and methods may be implementedto dissipate heat in multiprocessor computers or other electronicdevices caused by, e.g., physical location of semiconductor chips in thedevice housing, uneven loads on the processors, different operatingfrequencies, etc. If one or more processor (or other component) is notcooled as efficiently as other processors, thermal load balancing may beimplemented to assist in cooling the other processors.

In an exemplary embodiment, local heat sinks are thermally coupled toseparate processors in a multiprocessor computer, and at least one heatpipe thermally couples the heat sinks to one another in a heat sinknetwork. If one or more of the processors is generating more heat thanother processors, the excess heat is distributed via the heat pipe tothe other heat sinks in the heat sink network. Accordingly, smaller heatsinks may be implemented and efficiently used to dissipate heat. Inaddition, the computer system may have better acoustics because thecooling fan(s) do not have to operate as often and/or as fast. These andother exemplary embodiments will now be described in more detail withreference to the figures.

FIG. 1 is a high-level schematic illustration of an exemplary printedcircuit (PC) board which may implement thermal load balancing, e.g., ina computer system (not shown). In an exemplary embodiment, the computersystem may be a multiprocessor computer, e.g., commercially available asserver computers. However, the systems and methods described herein arenot limited to use with any particular type or configuration of computersystem.

Exemplary PC board 100 may be mounted within a housing (not shown) ofthe computer system, such as, e.g., a plastic or metal enclosuresuitable for desktop use or for mounting on a rack system. PC board 100may include one or more processing units or processors 110, 111. PCboard 100 may also include other system components, such as, e.g.,system memory 120 (e.g., read only memory (ROM) and random access memory(RAM)) and input/output (I/O) ports 130. A bus 140 couples the varioussystem components, including the system memory 120 and I/O ports 130, tothe processors 110, 111.

It is noted that PC board 100 may be implemented in a computer systemincluding other devices and components mounted to, connected to, orpositioned near the PC board 100. For example, computer systemstypically include data storage devices (e.g., hard disk drives, compactdisc (CD) or digital versatile disc (DVD) drives, etc.). The computersystems may also operate in a communications network, and thereforeinclude suitable network connection interface(s). These devices and/orinterfaces may be connected to the PC board, e.g., via bus 140. Stillother devices and components may also be mounted on or otherwiseconnected to the PC board 100, as is readily apparent to one havingordinary skill in the art.

During operation, one or more of these components (e.g., the processors110, 111) may generate heat. Accordingly, heat sinks 150, 151 may beprovided near or adjacent the components generating the heat to aid indissipating the heat. In an exemplary embodiment, the heat sinks 150,151 include blocks of thermally conductive material (e.g., metal ormetal alloys) configured to absorb and dissipate the heat generated byprocessors 110, 111. It is noted that there exist many different heatsinks, and the systems and methods described herein for thermal loadbalancing are not limited to any particular type or configuration ofheat sink.

Heat sinks 150, 151 may be thermally coupled to one another by one ormore heat pipe 160, in a configuration referred to herein as a heat sinknetwork 165. One or more cooling fans 170, 171 may also be provided toremove heat from the heat sinks 150, 151, e.g., by distributing heat tothe surrounding environment. It is noted that although only two heatsinks 150, 151 are shown in FIG. 1, any number of heat sinks may beimplemented for each of the processors. Likewise, any number of heatpipes and/or cooling fans may be implemented.

Each heat sink 150 and 151 functions locally to remove heat. Forexample, heat sink 150 removes heat generated by processor 110, and heatsink 151 removes heat generated by processor 111. The heat pipe 160enables thermal load balancing among the heat sinks 150 and 151.

By way of illustration, a multiprocessor computer may include twoprocessors (e.g., processors 110 and 111 in FIG. 1). During an exemplaryoperation, one of the processors generates 50 watts of heat, and thesecond processor generates 90 watts of heat. In a conventional computersystem, firmware and/or software may respond to any one of theprocessors generating over 75 watts of heat by increasing the fan speedfrom low to high, so as to avoid damaging the processors or other systemcomponents.

In the thermal load balancing system, however, the heat pipe 160distributes heat over the heat sink network (e.g., among the heat sinks150, 151), so that the average heat measured at either heat sink 150,151 is about 70 watts. Accordingly, the threshold for increasing the fanspeed from low to high is not reached in this example, and the coolingfan 170 continues to run at low speed. Not only does the cooling fanlast longer by running at low speed, it consumes less electricity andmakes less noise.

Thermal load balancing systems and methods may be implemented as a formof “self-regulation” in multiprocessor computers. For example, the heatsinks 150, 151 may be collectively sized to dissipate heat for any oneof the processors 110, 111 operating at full-power at any given time,but may be collectively undersized to dissipate heat if all of theprocessors 110, 111 are operating at full-power at about the same time.Accordingly, operation of the processors 110, 111 is constrained by theability to dissipate heat so that all of the processors 110, 111 cannotoperate at full power simultaneously, but at least any one processor(e.g., processor 110) can operate at full power at any given time.

Such an implementation enables the use of smaller heat sinks than wouldotherwise be necessary for full-power operation, thereby reducing cost,space consumed by the heat sinks 150, 151, and overall product weight.However, full-power operation for at least one of the processors 110 or111 at any given time is still possible.

Thermal load balancing may also be implemented to enable multipleprocessors 110, 111 to be installed in-line, even if one or more of theprocessors are in the draft of another processor. In a conventionalsystem, heat generated by in-line processors (e.g., processors installeddirectly adjacent one another) may overlap and adversely affectoperation if the heat sink is not large enough to compensate for theadditional, overlapping heat. However, thermal load balancing may beimplemented to deliver excess heat due to the overlap to other heatsinks in the heat sink network 165 so that the heat does not adverselyaffect operation of the in-line processors.

In addition, thermal load balancing may also be implemented tocompensate for slight misalignment of the processors 110, 111 and theheat sinks 150, 151 relative to one another. In a conventional system,the heat sinks may be sized based on a predetermined positioning of theheat sink adjacent the processor. If a heat sink is misaligned (e.g.,positioned too close to the processor or too close another heatgenerating device), the heat sink may absorb more heat than it isdesigned for. Thermal load balancing compensates for such misalignmentby delivering excess heat to other heat sinks in the heat sink network165.

FIGS. 2-4 are high-level schematic illustrations of other exemplaryembodiments of thermal load balancing. It is noted that 200-, 300-, and400-series reference numbers are used to refer to corresponding elementsin FIG. 1, and may not be described again with reference to FIGS. 2-4.In addition, the bus (e.g., bus 130 in FIG. 1) is not shown in FIGS. 2-4for purposes of clarity.

FIG. 2 shows a PC board 200 having a number of processors 210, 211, and212. Individual heat sinks 250, 251, and 252 are provided to locallyremove heat generated by each of the processors 210-212, respectively.The heat sinks 250-252 are thermally coupled to one another by heat pipe260 to form a heat sink network 265.

In an exemplary embodiment, one of the processors (e.g., processor 212)may be thermally disadvantaged as a result of its position on the PCboard 200. For example, processor 212 is positioned in a corner of thePC board 200 adjacent memory 220 and the computer housing (not shown).In addition, cooling fans 270, 271 may not assist heat sink 252 byreason of the relative position of the cooling fans 270, 271 to heatsink 252.

In a conventional system the processor 212 may need to be provided witha larger heat sink than would otherwise be required in order toeffectively remove heat generated by the processor 212 due to theposition of the processor 212 on the PC board 200. However, thermal loadbalancing enables excess heat to be delivered via the heat pipe 260 tothe other heat sinks 251, 250 in the heat sink network 265 toeffectively dissipate heat.

FIG. 3 shows a PC board 300 having a number of processors 310, 311, and312. Individual heat sinks 350, 351, and 352 are provided to locallyremove heat generated by each of the processors 310-312, respectively.The heat sinks 350-352 are thermally coupled to one another by heat pipe360 to form heat sink network 365.

In a conventional system, each heat sink may need to be sized for aworst-case scenario, e.g., to remove heat from the correspondingprocessor operating at full power. However, thermal load balancingenables the heat sinks 350-352 to be collectively sized to remove heatfor a worst-case scenario (e.g., one or more of the processors operatingat full power), without having to size all of the heat sinks for aworst-case scenario. Instead, the heat sink network collectively (or asa whole) provides sufficient capacity to remove heat if one or more ofthe processors is operating at full power.

It is appreciated that the heat sinks 350-352 may therefore be sizedmore efficiently. For example, processors which typically generate moreheat may be provided with a larger heat sink than processors whichtypically generate less heat. By way of illustration, heat sink 351 isshown sized larger than heat sink 350, and heat sink 352 is shown sizedlarger than both heat sinks 350 and 351. But if one of the otherprocessors (e.g., processor 310) generates more heat than was predictedduring design, excess heat is distributed to other heat sinks in theheat sink network 365 (e.g., heat sinks 351, 352).

FIG. 4 shows a PC board 400 having a number of processors 410, 411, and412. Individual heat sinks 450, 451, and 452 are provided to locallyremove heat generated by each of the processors 410-412, respectively.The heat sinks 450-452 are thermally coupled to one another by heat pipe460 to form heat sink network 465.

The heat sink network 465 may also include a master heat sink 480.Master heat sink 480 may be thermally coupled to the other heat sinks410-412, e.g., via heat pipe 460. In an exemplary embodiment, the masterheat sink 480 is provided outside of a thermal boundary 490. The term“thermal boundary” is used herein to describe a physical area that is ata higher temperature than the surrounding area. Also in an exemplaryembodiment, the master heat sink 480 may be thermally coupled to one ormore cooling fan 470. Accordingly, master heat sink 480 may beimplemented to more effectively and quickly remove heat than mightotherwise be possible by the local heat sinks 450-452 alone.

It is noted that the exemplary embodiments discussed above are providedfor purposes of illustration. Still other embodiments are alsocontemplated. It is also noted that, although the systems and methodsare described with reference to computer systems, in other exemplaryembodiments, thermal load balancing may be implemented for otherelectronic devices, such as, e.g., peripheral devices for computers,video and audio equipment, etc.

In addition to the specific embodiments explicitly set forth herein,other aspects and embodiments will be apparent to those skilled in theart from consideration of the specification disclosed herein. It isintended that the specification and illustrated embodiments beconsidered as examples only.

1. A thermal load balancing system for a multiprocessor computer havinga plurality of processors, comprising: a heat sink network having aplurality of local heat sinks, the local heat sinks thermally coupled toseparate processors in the multiprocessor computer wherein the heat sinknetwork is collectively undersized to dissipate heat if all of theprocessors operate at full-power at about the same time; and at leastone heat pipe thermally coupling each of the plurality of local heatsinks in the heat sink network.
 2. The system of claim 1 wherein theheat sink network includes a one-to-one correspondence of local heatsinks to separate processors.
 3. The system of claim 1 wherein at leasttwo processors are positioned in-line with one another.
 4. The system ofclaim 1 wherein at least two of the plurality of local heat sinks aredifferent sizes relative to one another.
 5. The system of claim 1wherein at least one of the plurality of local heat sinks is undersizedfor dissipating heat during full-power operation of at least one of theprocessors.
 6. The system of claim 1 wherein the heat sink network iscollectively sized to dissipate heat for any one of the processorsoperating at full-power at any given time.
 7. The system of claim 1wherein the heat sink network dissipates heat from at least oneprocessor in a thermally disadvantageous physical location.
 8. Thesystem of claim 1 further comprising at least one master heat sinkthermally coupled to the heat sink network, the master heat sinkpositioned outside a thermal boundary around the processors.
 9. Thesystem of claim 8 further comprising at least one cooling fan thermallycoupled to the master heat sink.
 10. A method of thermal load balancing,comprising: absorbing heat from each processor in a multiprocessorcomputer at local heat sinks; distributing heat from the local heatsinks over a heat sink network to substantially balance thermal loadingon the local heat sinks; and sizing the heat sink network to preventfull-power operation of all the processors at about the same time. 11.The method of claim 10 wherein distributing heat from the local heatsinks is at least in part to a master heat sink in the heat sinknetwork.
 12. The method of claim 10 further comprising compensating forthermal effects of a misaligned local heat sink and processor.
 13. Themethod of claim 10 wherein absorbing heat is from different size localheat sinks.
 14. The method of claim 10 further comprising dissipatingheat during full-power operation of at least one processor even if atleast one of the local heat sinks is undersized for full-poweroperation.
 15. The method of claim 10 further comprising collectivelysizing the heat sink network to dissipate heat for any one processoroperating at full-power.
 16. The method of claim 10 further comprisingself-regulating full-power operation of the processors.
 17. A system forthermal load balancing, comprising: local heat-collection means forabsorbing heat from a plurality of components in an electronic devicewherein each heat-collection means is undersized for dissipating heat byitself; and heat-distribution means for distributing heat tosubstantially balance thermal loading of the local heat-collectionmeans.
 18. The system of claim 17 wherein at least two of the localheat-collection means are different sizes relative to one another.
 19. Athermal load balancing system for a multiprocessor computer having aplurality of processors, comprising: a heat sink network of local heatsinks thermally coupled to separate processors in the multiprocessorcomputer, the heat sink network collectively sized to dissipate heat forany one of the processors operating at full-power at any given time, andthe heat sink network collectively undersized to dissipate heat if allof the processors operate at full-power at about the same time; and atleast one heat pipe thermally coupling the local heat sinks together inthe heat sink network.
 20. The system of claim 19 wherein at least oneof the local heat sinks is undersized for dissipating heat by itselfduring full-power operation of at least one of the processors.